Vinyl halide resin compositions are widely used as packaging films, sheeting, hose and tubing, coatings, wire insulations, business machine and appliance parts and housings, synthetic textile garments and materials of construction, among other applications. It is, therefore, of considerable importance that such materials have good fire resistance. While polyvinyl chloride, vinyl chloride copolymers and vinylidene chloride homopolymers and copolymers do not readily burn under ordinary circumstances, they release toxic hydrochloric acid fumes when subjected to strong heat, and if after ignition the burning material continues to be exposed to the flames it can be consumed in the resultant combustion process. Other vinyl halide resins such as polyvinylbromide and polyvinylfloride similarly release toxic hydrogen halide fumes and can also be consumed by combustion in the presence of flames.
Vinyl halide resins are normally compounded with other materials that flexibilize, toughen, or stabilize them against degradation by heat and ultraviolet light. However, the use of such additives frequently increases the combustibility of the resins. This is true, for example, when adding plasticizers such as dioctyl phthalate or dioctyl adipate which impart enhanced flexibility, as well as when adding impact modifiers such as acrylonitrile butadiene styrene terpolymers.
Vinyl halide compositions have heretofore been rendered somewhat less combustible by incorporating therein materials such as phosphate ester plasticizers, antimony oxide, and phosphites or tin-containing stabilizers. However, these additives do not alleviate the problem of smoke generation which is in part attributable to the evolution of gases that burn with very smoky flames as well as to the release of toxic hydrohalide acid fumes. Further, such additives do not appreciably alleviate the problem of combustion of the polymer composition on being exposed to a flame.
It is an object of this invention to provide novel, fully compounded vinyl halide resin compositions which have improved fire resistance and which are free of many of the disadvantages associated with the use of previously available systems as they are subjected to combustion conditions. A more particular object is to provide a vinyl halide resin having a composition such that increased charring of the surface of the resin will occur when the said surface is subjected to heat by a flame. The nature of still other objects of the invention will be apparent from a consideration of the descriptive portion to follow.